Take a look the Available Disk Space readout at the bottom of the Cakewalk window. If it says you're low, then you're low, and you'll need to clean up some space. To do this, choose Tools | Clean Audio Disk. Click Find, and once all the files are located, choose Delete All. Make sure you empty your Windows recycle bin afterward, in case the files were sent there.If the disk space readout looks like you've got plenty of room, locate the file AUD.INI in the Cakewalk directory, and delete it.

Go to Options | Audio | Advanced, and make sure the Data Directory is pointing to the proper path. If you've recently reinstalled or upgraded Cakewalk, this may be incorrect and you'll have to edit it now. Alternately, you can change the Data Directory to C:\Wave (or whatever drive letter is appropriate for your system). If you've already recorded some audio in other files, be sure to move the contents of the previous Data Directory to this new one.

Make sure that the computer's date is set to the current date. Do this by going to Start | Settings | Control Panel | Date/Time, or by right-clicking on the taskbar's clock and choosing Adjust Date/Time.